A glue solution and a preparation method thereof, a separator containing the same, and a negative electrode sheet

Abstract

The application relates to the field of electrochemistry, and provides a glue solution, a preparation method thereof, a diaphragm containing the glue solution and a negative pole piece. The glue solution comprises a metal element doped metal organic framework material, a dispersing agent and a wetting agent, the metal element is selected from at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Ti, Zn and Mn, and the mole content of the metal element is 0 mol / mol to 2.3 mol / mol based on the amount of substance of the metal element doped metal organic framework material. The glue solution can solve the problem that the metal organic framework material is prone to agglomeration. The diaphragm coating slurry and the negative pole coating slurry using the glue solution have good dispersibility, uniformity and ionic conductivity at the same time, so that the overall performance of a secondary battery is improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a colloid and its preparation method, a diaphragm coating slurry using the colloid, a negative electrode coating slurry using the colloid, a diaphragm using the diaphragm coating slurry, and a negative electrode sheet using the colloid. Background Technology

[0002] Due to their high specific surface area and high reactive density of Lewis acid-base sites, nano-MOF materials are widely used in lithium-ion batteries. However, nano-MOF materials are extremely unstable and prone to aggregation, losing their original properties and reducing their value, posing challenges to the preparation and storage of nanomaterials. Currently, the main problem with composite coatings of nano-MOF functional materials lies in the dispersibility and uniformity of the coating slurry.

[0003] Therefore, how to improve the dispersion and uniformity of nano-MOF materials in processing slurries and increase the cross-interface transport rate of lithium ions to improve the overall performance of lithium-ion batteries has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this application is to provide a colloid and its preparation method, a separator coating slurry using the colloid, a negative electrode coating slurry using the colloid, a separator using the separator coating slurry, and a negative electrode sheet using the colloid; to solve the problem of easy agglomeration of nano-MOF materials when applied to slurries. Furthermore, the application of a colloid with good uniformity and dispersibility to the separator coating slurry and the negative electrode coating slurry can improve the metal ion trans-interface transport rate and improve the overall performance of the secondary battery. The specific technical solution is as follows:

[0005] The first aspect of this application provides a liquid comprising a metal-organic framework material doped with a metal element, a dispersant, and a wetting agent; wherein the metal-organic framework material doped with the metal element has the molecular formula M a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b, 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24; wherein, M is a metallic element, including at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Ti, Zn and Mn; OL is a dicarboxylic acid conjugated organic ligand, and sol includes acetate, formate, CH3-(CH2) p -COO - At least one of the following, 1≤p≤6, blank is a ligand vacancy, and N is a counter ion.

[0006] In one embodiment of this application, the molar ratio of Zr to OL in the adhesive solution is 6:(2.53~5.055).

[0007] In one embodiment of this application, the molar ratio of Zr to OL in the adhesive is 6:(2.766~4.64).

[0008] In one embodiment of this application, the molar ratio of Zr to OL in the adhesive solution is 6:(2.766~4.266).

[0009] In one embodiment of this application, the molar ratio of Zr to OL in the adhesive solution is 6:(2.766~3.69).

[0010] In one embodiment of this application, the total defect rate of the metal-organic framework material doped with the metal element is 20% to 53.5%.

[0011] In one embodiment of this application, the total defect rate of the metal-organic framework material doped with the metal element is 29.6% to 53.5%.

[0012] In one embodiment of this application, the total defect rate of the metal-organic framework material doped with the metal element is 40% to 53.5%.

[0013] In one embodiment of this application, the unsaturated coordination defect rate of the metal-organic framework material doped with the metal element is 15% to 50.1%.

[0014] In one embodiment of this application, the unsaturated coordination defect rate of the metal-organic framework material doped with the metal element is 26.1% to 50.1%.

[0015] In one embodiment of this application, the unsaturated coordination defect rate of the metal-organic framework material doped with the metal element is 37% to 50.1%.

[0016] In one embodiment of this application, 0.1 ≤ a ≤ 2.3.

[0017] In one embodiment of this application, based on the mass of the adhesive, the mass percentage of the metal-organic framework material doped with the metal element is 5% to 10%; the mass percentage of the dispersant is 0.1% to 1%; and the mass percentage of the wetting agent is 0.1% to 1%.

[0018] In one embodiment of this application, the dispersant comprises at least one of polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylonitrile; the wetting agent comprises at least one of 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,2-hexanediol, 1,2-octanediol, 2-methyl-2,4-pentanediol, 1,3-butanediol, sodium dodecyl sulfate, sodium dodecyl sulfonate, and kynediol polyoxyethylene ether.

[0019] In one embodiment of this application, the metal-organic framework material doped with the metal element is neutral.

[0020] In one embodiment of this application, the metal-doped metal-organic framework material includes a dicarboxylic acid conjugated organic ligand, wherein the molecular skeleton of the dicarboxylic acid conjugated organic ligand includes any one of phenyl, imidazolyl, and pyridinyl.

[0021] In one embodiment of this application, the molecular skeleton of the dicarboxylated conjugated organic ligand is selected from phenyl, and the dicarboxylated conjugated organic ligand includes functional groups, which include any one of amino, hydroxyl, mercapto, methoxy, nitro, fluorine, and chlorine groups.

[0022] In one embodiment of this application, the dicarboxylic acid conjugated organic ligand includes any one of terephthalate, amino-modified terephthalate, fluoroterephthalate, and pyridinic acid dicarboxylate.

[0023] In one embodiment of this application, the average particle size of the metal-organic framework material doped with the metal element is 20 nm to 110 nm.

[0024] In one embodiment of this application, the average particle size of the metal-organic framework material doped with the metal element is 64 nm to 80 nm.

[0025] The second aspect of this application provides a method for preparing the adhesive solution provided in the first aspect of this application, comprising: mixing the dispersant, the wetting agent, the metal-organic framework material doped with metal elements with a solvent, dispersing them evenly, and obtaining the adhesive solution.

[0026] A third aspect of this application provides a diaphragm coating slurry comprising a water-retaining agent, a binder, and the adhesive described in the first aspect of this application.

[0027] In one embodiment of this application, based on the mass of the diaphragm coating slurry, the mass percentage of the adhesive is 80% to 90%; the mass percentage of the water-retaining agent is 0.1% to 1%; and the mass percentage of the binder is 1% to 5%.

[0028] In one embodiment of this application, the water-retaining agent comprises sodium carboxymethyl cellulose, and the binder comprises at least one selected from polyacrylate, ethyl acrylate copolymer, butyl acrylate copolymer, styrene acrylate copolymer, acrylamide acrylate copolymer, maleic anhydride acrylate copolymer, vinylpyrrolidone acrylate copolymer, methyl methacrylate acrylate copolymer, acrylonitrile acrylate copolymer, vinyl alcohol acrylate copolymer, sodium carboxymethyl cellulose, and polyvinyl alcohol.

[0029] In one embodiment of this application, the viscosity of the diaphragm coating slurry is 20 cps to 100 cps, preferably 40 cps to 80 cps.

[0030] A fourth aspect of this application provides a diaphragm comprising a substrate and a first coating disposed on at least one surface of the substrate, the first coating comprising the diaphragm coating slurry described in the third aspect of this application.

[0031] In one embodiment of this application, the thickness of the first coating is 1μm to 5μm, preferably 1μm to 2μm.

[0032] In one embodiment of this application, the unit coating weight of the first coating is 0.1 g / m². 2 ~0.8g / m 2 The preferred value is 0.25 g / m 2 ~0.5g / m 2 .

[0033] The fifth aspect of this application provides a negative electrode coating slurry comprising the adhesive described in the first aspect of this application.

[0034] In one embodiment of this application, the negative electrode coating slurry includes a negative electrode active material, a conductive agent, and a binder; based on the mass of the negative electrode coating slurry, the mass percentage of the adhesive is 0.58%~22.6%; the mass percentage of the negative electrode active material is 38.2%~49.1%; the mass percentage of the conductive agent is 0.2%~3.5%; and the mass percentage of the binder is 1.5%~4.5%.

[0035] The sixth aspect of this application provides a negative electrode sheet comprising the negative electrode coating slurry described in the fifth aspect of this application.

[0036] In one embodiment of this application, the negative electrode sheet includes a negative current collector, a negative electrode material layer, and a second coating layer. The negative electrode material layer is disposed on at least one surface of the negative current collector, and the second coating layer is disposed on at least one surface of the negative electrode material layer. The second coating layer includes the adhesive liquid described in the first aspect of this application.

[0037] The beneficial effects of this application are:

[0038] This application provides a colloid, a membrane coating slurry and a negative electrode coating slurry using the colloid, a membrane using the membrane coating slurry, and a negative electrode sheet using the colloid. The colloid of this application comprises a metal-organic framework material doped with a metal element, a dispersant, and a wetting agent; the molecular formula of the metal-organic framework material doped with the metal element is M. a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b , 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24; where M is a metallic element, including at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Ti, Zn, and Mn; OL is a dicarboxylic acid conjugated organic ligand, and sol includes acetate, formate, and CH3-(CH2). p -COO - At least one of the following, 1≤p≤6, blank represents a ligand vacancy, and N represents a counter ion. The adhesive solution of this application includes metal-organic framework materials doped with metal elements, which not only leverages the advantages of metal-organic framework materials—facilitating the activity of metal ions (e.g., Li)—but also… + During interfacial transport, the removal of the coordinating solvent increases the rate of active metal ion transport across the interface; it also solves the problem of easy aggregation of metal-organic framework materials. The separator coating slurry and negative electrode coating slurry using the described adhesive simultaneously possess good dispersibility, uniformity, and ionic conductivity, thereby improving the overall performance of the secondary battery.

[0039] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0041] Figure 1 Here is a scanning electron microscope image of the diaphragm coating of Example 2-2;

[0042] Figure 2 These are scanning electron microscope (SEM) images of the diaphragm coatings in Examples 2-3;

[0043] Figure 3 These are scanning electron microscope (SEM) images of the diaphragm coatings in Examples 2-4;

[0044] Figure 4 The X-ray diffraction (XRD) patterns of the metal-organic framework materials doped with metal elements used in Examples 2-2 and 2-3, and the metal-organic framework materials without metal element doping. Detailed Implementation

[0045] The technical solutions of this application will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0046] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries in this application are not limited to lithium-ion batteries.

[0047] The first aspect of this application provides a liquid comprising a metal-organic framework material doped with a metal element, a dispersant, and a wetting agent; wherein the metal-organic framework material doped with the metal element has the molecular formula M a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b, 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24, preferably, 0.1≤a≤2.3, 0.16≤x≤0.3; wherein, M is a metallic element, including at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Ti, Zn and Mn; OL is a dicarboxylic acid conjugated organic ligand, and sol is selected from acetate, formate, CH3-(CH2). p -COO - At least one of the following, 1≤p≤6, blank is a ligand vacancy, and N is a counter ion. For example, the value of 'a' can be 0, 0.01, 0.05, 0.1, 0.3, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.3, or a range of any two values; the value of 'x' can be 0.09, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.92, or a range of any two values; the value of 'y' can be 1.8, 2, 2.2, 2.5, 2.6, 2.8, 2.9, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.88, 6.02, or a range of any two values. The value of b can be any two values ​​within a range; the value of b can be 0.9, 1.2, 1.5, 1.8, 1.9, 2.1, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.48, 5.5, 5.8, 6, 6.2, 6.55, 6.8, 7.02, 7.55, 8, 8.5, 9.24 or any two values ​​within a range; the value of m can be 4, 4.3, 4.6, 5, 5.2, 5.5, 5.8, 6 or any two values ​​within a range; the value of n can be 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4 or any two values ​​within a range.

[0048] Active metal ions (e.g., Li) +In secondary batteries, interfacial migration requires active metal ions to remove coordinating solvents. This process necessitates overcoming a high energy barrier of 50 kJ / mol to 70 kJ / mol for interfacial charge transfer. Therefore, compared to bulk transport within the electrodes and electrolyte, desolvation is generally considered the main energy-consuming step in the transport of active metal ions. The inventors have discovered that by including the metal-doped metal-organic framework (MOF) material of this application in the gel and controlling the molar content of the metal element within the range of this application, the advantages of the metal-doped MOF material can be fully utilized: the porous structure of the metal-doped MOF material facilitates the removal of active metal ions from the outer weakly coordinating solvent; the metal doping sites in the metal-doped MOF material promote the dissociation of the inner strong coordinating solvent of the active metal ions, and this "assembly line" synergistic desolvation mechanism improves the rate of interfacial transport of active metal ions; the abundant polar groups on the surface of the metal-doped MOF material have high affinity for the electrolyte, and the porous structure allows for rapid electrolyte conduction, which is beneficial for electrolyte wetting. Furthermore, due to the pore-confining effect of metal-organic framework materials doped with metal elements, TFSI in the electrolyte can be anchored. - FSI - PF6 - The presence of anions can release more active lithium ions, and faster ion transport can reduce the thickness of the positive electrode interface film and adjust the composition of the negative electrode interface film, further reducing the loss of active lithium due to the formation of the positive and negative electrode interface films. On the other hand, it can solve the problem of easy aggregation of nano-MOF materials. This is because the metal doping and high defect rate in the metal-organic framework doped with metal elements will aggravate the uneven distribution of local charge, which will further lead to the wetting agent anions being in a kinetically advantageous and more stable adsorption state near the metal sites. This is equivalent to planting a protective layer on the surface of a single MOF particle. The protective layer and the dispersant are entangled with each other, which enhances the interaction between the dispersant and the particles, ultimately resulting in excellent dispersion.

[0049] In this application, the metal element-doped metal-organic framework (MOF) material is a compound containing a metal element, where the metal element is doped into the crystal structure of the MOF material. That is, the metal element is chemically modified into the crystal structure of the MOF material, and its crystal structure changes after doping. The metal element-doped MOF material provided in this application differs from physically adsorbing a metal element into the MOF material. If a metal element is physically adsorbed into the MOF material, during the charging and discharging process of the secondary battery, the physically adsorbed metal element will detach from the pores of the MOF material. As the electric field diffuses to the electrode interface, it can catalyze side reactions such as gas production, affecting the electrochemical performance of the secondary battery. It also differs from physically mixing a metal compound and the MOF material. In physical mixing, the contact between the metal compound (such as oxides or nanoparticles) and the MOF crystal is only a macroscopic interface, and molecular-scale bonding or electronic coupling cannot be formed. There is a clear phase separation between the phases, and it is difficult for molecular-scale synergy to exist between them. The reactants are difficult to transport efficiently between the two phases, resulting in low efficiency of synergistic catalytic dissociation, interfacial charge transfer, or adsorption-catalytic degradation of harmful byproducts in cascade reactions.

[0050] 'a' represents the amount of substance of the metal-organic framework material based on metal element doping, specifically the molar content of the metal element. When 'a' is too large, for example, greater than 2.3, some metal elements are adsorbed into the pores of the metal-organic framework material in the form of physical adsorption. During the charging and discharging process of the secondary battery, these metal elements will detach from the pores of the metal-organic framework material and diffuse to the electrode interface with the electric field, catalyzing side reactions such as gas production, which will affect the electrochemical performance of the secondary battery.

[0051] In one embodiment of this application, the molar ratio of Zr to OL in the adhesive is 6:(2.53~5.055), preferably 6:(2.766~4.64), more preferably 6:(2.766~4.266), and even more preferably 6:(2.766~3.69). For example, the molar ratio of Zr to OL can be 6:2.53, 6:2.766, 6:3.5, 6:3.69, 6:4.266, 6:4.64, 6:5.055, or a range consisting of any two of these values. The molar ratio of Zr to OL actually reflects the total defect rate of the material. Theoretically, the total defect rate = 1 - n(OL) / n(Zr). Controlling the molar ratio of Zr to OL within the range of this application helps to ensure that the defect rate is within a suitable range, which can promote the removal of coordination solvents from active metal ions, increase the rate of cross-interface transport of active metal ions, improve the fast charging performance, cycle performance, and low-temperature performance of secondary batteries, and help to improve the energy density of secondary batteries.

[0052] In one embodiment of this application, thermogravimetric analysis is used to test the total defect rate of the metal-doped metal-organic framework material, which is 20% to 53.5%, preferably 29.6% to 53.5%, and more preferably 40% to 53.5%. For example, the total defect rate of the metal-doped metal-organic framework material can be 20%, 22%, 25%, 29.6%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 45%, 47%, 49%, 50%, 53.5%, or a range of any two of these values. Defects in MOF materials possess unique spatial structures and electronic properties, which can provide active sites for chemical reactions. The total defect rate refers to the ratio of the number of defects present in the structure of the metal-organic framework material to the number of corresponding connecting ligands in the theoretically intact structure. If the ligand is not completely connected to the metal node or if the structure of the ligand itself (such as length, functional groups, molecular skeleton, etc.) is altered, organic ligand defects will be formed. For example, in a metal-organic framework material with terephthalic acid as a ligand, terephthalic acid may be partially missing in coordination or replaced by solvents and template agents, resulting in organic ligand defects.

[0053] In one embodiment of this application, solid-state NMR phosphorus spectroscopy is used for testing. The unsaturated coordination defect rate of the metal-doped metal-organic framework material is 15%~50.1%, preferably 26.01%~50.1%, and more preferably 37%~50.1%. For example, the unsaturated coordination defect rate of the metal-doped metal-organic framework material can be 15%, 18%, 20%, 22%, 24%, 25%, 26.01%, 28%, 29%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50.1%, or a range consisting of any two of these values. Compared with other types of defects, unsaturated coordination defects have higher activity. Exposed unsaturated metal sites have lower steric hindrance and higher site accessibility, which is more conducive to active metal ions (e.g., Li). + During interfacial transport, the coordination solvent is removed. Furthermore, unsaturated coordination sites typically have lower metal valence states, resulting in a charge distribution within the material and a charge transfer path with the substrate that differs significantly from saturated coordination structures. This unique charge distribution and transfer path are more conducive to molecular activation and electron migration, thereby increasing the rate of interfacial transport of active metal ions. Limiting the unsaturated coordination defect rate of metal-organic framework materials doped with metal elements to the range described in this application is beneficial for improving the rate of interfacial transport of active metal ions in secondary batteries and enhancing the overall performance of the secondary battery.

[0054] In one embodiment of this application, based on the mass of the adhesive, the mass percentage of the metal-organic framework material doped with the metal element is 5% to 10%; the mass percentage of the dispersant is 0.1% to 1%; and the mass percentage of the wetting agent is 0.1% to 1%. For example, the mass percentage of the metal-organic framework material doped with the metal element can be 5%, 6%, 7%, 8%, 9%, 10%, or any two of these values; the mass percentage of the dispersant can be 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, or any two of these values; and the mass percentage of the wetting agent can be 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, or any two of these values. Limiting the mass percentages of the metal-organic framework material doped with the metal element, the dispersant, and the wetting agent to the ranges specified in this application can improve the stability of the adhesive.

[0055] In one embodiment of this application, the dispersant comprises at least one selected from polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylonitrile; the wetting agent comprises at least one selected from 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,2-hexanediol, 1,2-octanediol, 2-methyl-2,4-pentanediol, 1,3-butanediol, sodium dodecyl sulfate, sodium dodecyl sulfonate, and kyne glycol polyoxyethylene ether. Using the dispersant of this application is beneficial for stabilizing metal-doped metal-organic framework materials and reducing the agglomeration of metal-doped metal-organic framework materials in the slurry; using the wetting agent of this application is beneficial for the uniform distribution of the adhesive during coating.

[0056] In this application, the adhesive liquid includes a solvent selected from at least one of deionized water, N,N-dimethylformamide (DMF), and N-methylpyrrolidone (NMP).

[0057] In one embodiment of this application, the metal-doped metal-organic framework material is neutral. The acidity or alkalinity of the metal-doped metal-organic framework material is adjusted by a neutralizing agent selected from at least one of LiOH, NaOH, KOH, Zn(OH)2, Na2CO3, K2CO3, and Li2CO3. The inventors discovered in their research that, on the one hand, metal-organic framework materials doped with low-size metal elements are generally acidic due to the partial absence of organic ligands. However, most binders suitable for aqueous slurries are neutral or alkaline. Acidic conditions can cause the binder to denature, leading to slurry flocculation. Therefore, a neutralizing agent is needed to adjust the metal-doped metal-organic framework material to be neutral and prevent slurry flocculation. On the other hand, the neutralizing agent of this application, after consumption, only introduces a small amount of metal ions into the system without introducing other impurities. Depending on the battery system used for the separator, a corresponding neutralizing agent can be selected (e.g., LiOH in lithium-ion batteries and NaOH in sodium-ion batteries). This allows a small amount of metal ions to be absorbed into the interior of the metal-doped metal-organic framework material without causing a sudden drop in surface zeta potential due to the introduction of ions. Using the neutralizing agent of this application can improve the denaturation of the binder under acidic conditions, which helps the particles to disperse uniformly in the aqueous slurry, prevents agglomeration, improves the uniformity and stability of the slurry, and thus improves the electrochemical performance of the secondary battery.

[0058] In this application, the concentration of the neutralizing agent is not particularly limited, as long as it achieves the purpose of this application; for example, it can be 0.01 g / mL to 0.03 g / mL. Using a neutralizing agent within the above concentration range can better prevent the decomposition of metal-organic framework materials doped with some metal elements under strongly alkaline conditions.

[0059] In one embodiment of this application, the metal-doped metal-organic framework material includes a dicarboxylic acid conjugated organic ligand, the molecular skeleton of which includes any one of phenyl, imidazolyl, and pyridyl groups. When the molecular skeleton of the dicarboxylic acid conjugated organic ligand is selected from phenyl, the molecule itself has a certain rigidity, supporting only axial rotation of the molecule, which is beneficial for exerting the confinement effect of the pore size. When the molecular skeleton of the dicarboxylic acid conjugated organic ligand is selected from imidazolyl and pyridyl groups, the organic ligand skeleton itself contains heteroatoms, which is beneficial for adjusting the polarity of the pore wall of the metal-doped metal-organic framework material, thereby enhancing the interaction between its pore wall and lithium ions, solvent, and anions in the electrolyte, promoting the dissociation of the three within the pore, and thus improving the migration efficiency of lithium ions.

[0060] In one embodiment of this application, the molecular skeleton of the dicarboxylated conjugated organic ligand is selected from phenyl, and the dicarboxylated conjugated organic ligand includes functional groups, which include any one of amino, hydroxyl, mercapto, methoxy, nitro, fluorine, and chlorine groups; preferably, the functional group is selected from any one of amino, mercapto, and fluorine groups. Introducing functional groups into metal-organic framework materials doped with metal elements, and controlling the types of functional groups within the scope of this application, is beneficial for adjusting the polarity of the pore wall, thereby enhancing the interaction between the pore wall and lithium ions, solvent, and anions in the electrolyte, promoting the dissociation of the three within the pore, and thus improving the migration efficiency of lithium ions and the overall performance of the secondary battery.

[0061] In some embodiments of this application, the dicarboxylated conjugated organic ligand comprises at least one of the following substances:

[0062] (1) When the functional group is amino, the dicarboxylic acid conjugated organic ligand includes at least one of 2-aminoterephthalate, 2,5-diaminoterephthalate, 2,3-diaminoterephthalate, 2,3,5-triaminoterephthalate and 2,3,4,5-tetraaminoterephthalate; preferably at least one of 2-aminoterephthalate and 2,5-diaminoterephthalate.

[0063] (2) When the functional group is hydroxyl, the dicarboxylic acid conjugated organic ligand includes at least one of 2-hydroxyterephthalate, 2,5-dihydroxyterephthalate, 2,3-dihydroxyterephthalate, 2,3,5-trihydroxyterephthalate and 2,3,4,5-tetrahydroxyterephthalate.

[0064] (3) When the functional group is thiol, the dicarboxylic acid conjugated organic ligand includes at least one of 2-mercapto-terephthalate, 2,5-dimercapto-terephthalate, 2,3-dimercapto-terephthalate, 2,3,5-trimercapto-terephthalate and 2,3,4,5-tetramercapto-terephthalate;

[0065] (4) When the functional group is methoxy, the dicarboxylic acid conjugated organic ligand includes at least one of 2-methoxyterephthalate, 2,5-dimethoxyterephthalate, 2,3-dimethoxyterephthalate, 2,3,5-trimethoxyterephthalate and 2,3,4,5-tetramethoxyterephthalate;

[0066] (5) When the functional group is nitro, the dicarboxylic acid conjugated organic ligand includes at least one of 2-nitroterephthalate, 2,5-dinitroterephthalate, 2,3-dinitroterephthalate, 2,3,5-trinitroterephthalate and 2,3,4,5-tetranitroterephthalate;

[0067] (6) When the functional group is a fluorine group, the dicarboxylic acid conjugated organic ligand includes at least one of 2,5-dicarboxyfluorobenzoate, 2,5-difluoroterephthalate, 2,3-difluoroterephthalate, 2,3,5-trifluoroterephthalate and 2,3,4,5-tetrafluoroterephthalate; preferably 2,5-dicarboxyfluorobenzoate;

[0068] (7) When the functional group is a chlorine group, the dicarboxylic conjugated organic ligand includes at least one of 2,5-dicarboxychlorophthalate, 2,5-dichloroterephthalate, 2,3-dichloroterephthalate, 2,3,5-trichloroterephthalate and 2,3,4,5-tetrachloroterephthalate.

[0069] In some embodiments of this application, the molecular skeleton is selected from either pyridyl or imidazolyl, and the dicarboxylated conjugated organic ligand comprises at least one of the following substances:

[0070] (1) When the molecular skeleton is selected from pyridinyl, the dicarboxylic acid conjugated organic ligand includes 2,5-pyridinic acid dicarboxylate;

[0071] (2) When the molecular skeleton is selected from imidazole, the dicarboxylic conjugated organic ligand includes at least one of 1H-imidazol-2,4-dicarboxylate and imidazol-4,5-dicarboxylate.

[0072] In one embodiment of this application, the dicarboxyl conjugated organic ligand comprises any one of terephthalate, amino-modified terephthalate, fluoroterephthalate, and pyridinic acid dicarboxylate. The amino-doped terephthalate is selected from at least one of 2-aminoterephthalate, 2,5-diaminoterephthalate, 2,3-diaminoterephthalate, 2,3,5-triaminoterephthalate, and 2,3,4,5-tetraaminoterephthalate; preferably 2-aminoterephthalate or 2,5-diaminoterephthalate. The fluoroterephthalate ion is selected from at least one of 2,5-dicarboxyfluorobenzoate, 2,5-difluoroterephthalate, 2,3-difluoroterephthalate, 2,3,5-trifluoroterephthalate, and 2,3,4,5-tetrafluoroterephthalate; preferably 2,5-dicarboxyfluorobenzoate. The pyridine dicarboxylate ion is selected from 2,5-pyridine dicarboxylate. Metal-doped metal-organic framework materials, including dicarboxylic acid conjugated organic ligands within the above-mentioned range, are beneficial for further regulating the polarity of the pore walls of the metal-doped metal-organic framework materials, thereby enhancing the interaction between the pore walls and lithium ions, solvents, and anions in the electrolyte, promoting the dissociation of these three components within the pores, further improving the migration efficiency of lithium ions, and enhancing the overall performance of the secondary battery.

[0073] Zirconium-oxygen cluster nodes in UiO series metal-organic frameworks are typically represented as Zr6O4(OH)4 (i.e., m=4, n=4), a designation widely accepted in the industry. However, during post-processing such as heating and vacuum treatment, the hydroxyl groups at the zirconium-oxygen cluster nodes may dehydrate and partially detach, potentially forming a Zr6O6 structure in extreme cases. Due to limitations in current characterization techniques, the hydroxyl content at the zirconium-oxygen cluster nodes cannot be precisely quantified. Therefore, in this application, the molecular formula of the metal-doped metal-organic framework material is expressed as "M". a Zr6O m (OH) n (OL) 6(x+y) / 2 (sol) x (blank) y N b ", where 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 1.8≤y≤6.02, 0.9≤b≤9.24.

[0074] In this application, sol refers to a small molecule ligand, and blank refers to a ligand vacancy appearing around Zr. Sol is introduced during the preparation process via a template agent. It is understood that sol may be partially substituted by the solvent during preparation, for example, by polar molecules such as ethanol, dichloromethane, or water. It should be noted that when sol is selected from acetate in the embodiments of this application, this includes the case where it is partially substituted by the solvent.

[0075] In this application, since the metal-doped metal-organic framework material uses raw materials such as solvents and template agents in the preparation process, the prepared metal-doped metal-organic framework material also includes other adsorbed components, which include adsorbed solvents and / or adsorbed template agents; this application does not specifically limit the types and contents of other adsorbed components.

[0076] In some embodiments of this application, the counter ion is selected from PO4. 3- NO3 - Cl - SO4 2- ,Br - F - And any one of acetylacetonate. Preferably, the counterion is selected from PO4. 3- NO3 - Cl -Based on their charge characteristics, metal-organic frameworks (MOFs) can be classified into cationic frameworks, anionic frameworks, and neutral frameworks. Counterions, through non-covalent interactions, weakly bind to the MOFs and are essential for maintaining the charge neutrality of MOF materials. In this application, the metal-doped MOF material consists of a cationic framework and counterions. For the cationic framework of the metal-doped MOF material in this application, the counterions can originate from the MOF material preparation process or from the metal element loading process. In secondary batteries, the counterions in the metal-doped MOF material can dissolve and replace other ions with the same charge in the electrolyte, such as TFSI. - FSI - and PF6 - Counterions can affect the formation of the negative electrode film. The solid electrolyte interphase (SEI) film formed is more conducive to ion transport, thereby improving the charge transfer at the interface and improving the overall performance of the secondary battery.

[0077] In some embodiments of this application, the average particle size of the metal-doped metal-organic framework material is 20 nm to 110 nm, preferably 64 nm to 110 nm. For example, the average particle size of the metal-doped metal-organic framework material can be 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 110 nm, or any combination of two such values; the value of 'a' in the molecular formula can be 0, 0.01, 0.05, 0.1, 0.3, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.3, or any combination of two such values. Limiting the average particle size of the metal-doped metal-organic framework material to the range specified in this application is beneficial for increasing the surface exchange sites per unit mass of the metal-doped metal-organic framework material, promoting the removal of coordination solvents by active metal ions, increasing the rate of cross-interface transport of active metal ions, and improving the overall performance of the secondary battery.

[0078] When the particle size of a material is too large, the bulk diffusion paths of its ions / molecules increase significantly, resulting in slow mass transfer kinetics; simultaneously, the specific surface area decreases sharply, leading to an insufficient number of effective surface reaction sites. Both of these factors jointly limit the material's performance. Correspondingly, larger particle sizes usually mean higher crystallinity and a more complete structure, thus resulting in a lower total defect rate, especially a scarcity of highly reactive unsaturated coordination defects. When the particle size is too small, on the one hand, the surface energy is too high, making agglomeration highly likely, which reduces the effective surface area; on the other hand, excessively high defect density (especially a large number of unsaturated coordination defects) may disrupt the long-range ordered structure of the material, leading to decreased structural stability and potentially inducing the continuous occurrence of side reactions. Therefore, while small particle size significantly increases both the total defect rate and the unsaturated coordination defect rate, it also introduces the risks of agglomeration and structural instability.

[0079] In this application, the specific surface area of ​​the metal-organic framework material doped with metal elements is not particularly limited, as long as the purpose of this application can be achieved. For example, the specific surface area of ​​the metal-organic framework material doped with metal elements can be 400 m². 2 / g to 1040m 2 / g, limiting the specific surface area of ​​the metal-organic framework material doped with metal elements to the range of this application is beneficial for constructing suitable pore sizes, promoting the removal of coordination solvents from active metal ions, improving the rate of cross-interface transport of active metal ions, and improving the overall performance of secondary batteries.

[0080] In some embodiments of this application, the XRD patterns of the metal-doped metal-organic framework material include diffraction peaks on the (200) and (111) crystal planes. The inclusion of diffraction peaks on the (200) and (111) crystal planes in the XRD patterns of the metal-doped metal-organic framework material indicates, on the one hand, that the metal-doped metal-organic framework material used in this application still maintains a good crystal structure; on the other hand, it indicates that the metal-doped metal-organic framework material used in this application has a porous structure, with 8 Å pores arranged in an orderly manner within the framework. During the charging and discharging process of a secondary battery, under the action of an electric field, solvated lithium ions in the electrolyte pass through the coating. Under the confinement effect of the nanopores, the lithium ions undergo a gradient desolvation process. Compared with one-step desolvation on the positive and negative electrode surfaces, this gradient desolvation process requires overcoming a lower energy barrier.

[0081] In this application, the source of the metal-doped metal-organic framework material is not particularly limited; it can be obtained by purchase or by preparation. The preparation method of the substrate metal-organic framework material is not particularly limited, as long as it achieves the purpose of this application. For example, the preparation method of Zr-based metal-organic framework material may include, but is not limited to, the following steps: adding Zr source material and dicarboxylic acid conjugated organic ligand to deionized water and a template agent, stirring and refluxing, centrifuging to obtain a precipitate, soaking the precipitate in an organic solvent, and finally centrifuging to obtain the substrate metal-organic framework material. The preparation method of metal-doped metal-organic framework material is not particularly limited. For example, the preparation method of metal-doped Zr-based metal-organic framework material may be: drying and activating the Zr-based metal-organic framework material prepared above, adding a diffusion solvent to the activated Zr-based metal-organic framework material and the metal source material, refluxing, centrifuging, washing, and vacuum drying to obtain the metal-doped Zr-based metal-organic framework material. Other metal-based metal-organic framework materials can be prepared using methods similar to the above process, or they can be prepared using methods known to those skilled in the art or purchased from commercially available products, and then loaded with metal elements.

[0082] For Zr-based metal-organic framework materials, this application does not specifically limit the Zr source mentioned above, as long as it achieves the purpose of this application. For example, the Zr source material may include, but is not limited to, at least one of zirconium oxynitrate, zirconium chloride, zirconium oxychloride, zirconium bromide, zirconium fluoride, zirconium acetylacetonate, and zirconium sulfate. This application does not specifically limit the template agent mentioned above. For example, the template agent may include glacial acetic acid, formic acid, hydrochloric acid, and CH3-(CH2). p At least one of -COOH, 1≤p≤6. This application does not specifically limit the organic solvents mentioned above; for example, the organic solvent may include, but is not limited to, at least one of ethanol, acetone, and dichloromethane. This application does not specifically limit the metal element source material; for example, when the metal element is Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Ti, Zn, or Mn, a nitrate compound containing the corresponding metal element, a chloride compound containing the corresponding metal element, a sulfate compound containing the corresponding metal element, or a phosphate compound containing the corresponding metal element may be added accordingly. The selection can be made according to actual needs, as long as the purpose of this application is achieved. This application does not specifically limit the diffusion solvent; for example, the diffusion solvent may include, but is not limited to, at least one of deionized water, ethanol, methanol, n-hexane, cyclohexane, and acetone.

[0083] Typically, the molar content of metal elements in metal-organic framework materials doped with metal elements can be controlled by adjusting the concentration of the metal element source material. Combined with the "test of molar content of metal elements in metal-organic framework materials doped with metal elements" provided in this application, the desired metal-organic framework material doped with metal elements can be selected.

[0084] The second aspect of this application provides a method for preparing the adhesive solution provided in the first aspect of this application, which includes: mixing a dispersant, a wetting agent, a metal-organic framework material doped with metal elements with a solvent, dispersing them evenly, and obtaining an adhesive solution.

[0085] In this application, the method of uniform dispersion includes, but is not limited to, simultaneous ultrasonication and stirring. This application does not impose any particular limitations on the equipment used for ultrasonication and stirring, as well as the power and frequency of the ultrasonication, the stirring speed, and the duration of simultaneous ultrasonication and stirring, as long as the purpose of this application is achieved. For example, an ultrasonic cleaner and a mechanical stirrer can be used for simultaneous ultrasonication and stirring. The ultrasonic power can be 80W~120W, the frequency can be 20kHz~60kHz, the stirring speed can be 340r / min~380r / min, and the duration of simultaneous ultrasonication and stirring can be 1h~5h.

[0086] A third aspect of this application provides a diaphragm coating slurry comprising a water-retaining agent, a binder, and the adhesive described in the first aspect of this application.

[0087] In one embodiment of this application, based on the mass of the separator coating slurry, the mass percentage of the adhesive is 80%~90%; the mass percentage of the water-retaining agent is 0.1%~1%; and the mass percentage of the binder is 1%~5%. For example, based on the mass of the separator coating slurry, the mass percentage of the adhesive can be 80%, 82%, 84%, 86%, 88%, 90%, or any two of these values; the mass percentage of the water-retaining agent can be 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, or any two of these values; and the mass percentage of the binder can be 1%, 2%, 3%, 4%, 5%, or any two of these values. Limiting the mass percentages of the adhesive, water-retaining agent, and binder to the ranges specified in this application is beneficial for stabilizing the metal-doped metal-organic framework material, reducing the agglomeration of the metal-doped metal-organic framework material in the slurry, ensuring uniform dispersion of the slurry, and improving the overall performance of the secondary battery.

[0088] In one embodiment of this application, the water-retaining agent comprises sodium carboxymethyl cellulose, and the binder comprises at least one selected from polyacrylate, ethyl acrylate copolymer, butyl acrylate copolymer, styrene acrylate copolymer, acrylamide acrylate copolymer, maleic anhydride acrylate copolymer, vinylpyrrolidone acrylate copolymer, methyl methacrylate acrylate copolymer, acrylonitrile acrylate copolymer, vinyl alcohol acrylate copolymer, sodium carboxymethyl cellulose, and polyvinyl alcohol. The water-retaining agent is used to inhibit water evaporation, preventing component changes due to water evaporation during processing and improving product consistency. The binder is used to bond the metal-doped metal-organic framework material to the base film, preventing detachment. Using the water-retaining agent and binder of this application is more conducive to stabilizing the metal-doped metal-organic framework material, reducing the agglomeration of the metal-doped metal-organic framework material in the slurry, making the slurry uniformly dispersed, and improving the overall performance of the secondary battery.

[0089] In this application, the diaphragm coating slurry includes a solvent selected from at least one of deionized water, N,N-dimethylformamide (DMF), and N-methylpyrrolidone (NMP). It should be noted that the solvent in the diaphragm coating slurry is the same as that in the adhesive solution.

[0090] In one embodiment of this application, the viscosity of the separator coating slurry is 20 cps to 100 cps, preferably 40 cps to 80 cps. For example, the viscosity of the separator coating slurry can be 20 cps, 30 cps, 40 cps, 50 cps, 60 cps, 70 cps, 80 cps, 90 cps, 100 cps, or a range of any two of these values. Limiting the viscosity of the separator coating slurry to the range specified in this application can reduce the agglomeration of metal-doped metal-organic framework materials in the slurry, making the slurry more uniformly dispersed and improving the overall performance of the secondary battery.

[0091] In this application, the preparation method of the diaphragm coating slurry is not particularly limited, as long as it achieves the purpose of this application. For example, the preparation method of the diaphragm coating slurry includes: adding a water-retaining agent, a binder, and a solvent to a glue solution, mixing, and stirring to obtain the diaphragm coating slurry. The stirring is selected from at least one of ultrasonic stirring and ball milling. If acidic conditions will denature the binder, the metal-organic framework material doped with metal elements needs to be adjusted to neutral before preparing the glue solution.

[0092] In this application, the conditions for ultrasonic stirring include: ultrasonic power of 80W~120W, frequency of 20kHz~60kHz; stirring speed of 340r / min~380r / min; and ultrasonic stirring time of 1h~5h. For example, the ultrasonic power can be 80W, 90W, 100W, 110W, 120W, or any combination of two of these values; the frequency can be 20kHz, 30kHz, 40kHz, 50kHz, 60kHz, or any combination of two of these values; the stirring speed can be 340r / min, 350r / min, 360r / min, 370r / min, 380r / min, or any combination of two of these values; and the ultrasonic stirring time can be 1h, 2h, 3h, 4h, 5h, or any combination of two of these values. The ultrasonic stirring equipment is selected from ultrasonic cleaners and mechanical stirrers. Limiting the ultrasonic stirring conditions to the scope of this application is beneficial for stabilizing metal-doped metal-organic framework materials and can further disperse the slurry, preventing particle agglomeration and thus improving the overall performance of the secondary battery.

[0093] A fourth aspect of this application provides a separator comprising a substrate and a first coating disposed on at least one surface of the substrate, the first coating comprising the separator coating slurry described in the third aspect of this application. The separator coating slurry of this application exhibits good stability, and the separator prepared using it possesses excellent ionic conductivity, which can reduce the internal resistance of the battery and improve the charge-discharge efficiency of the battery. Furthermore, the separator coating slurry of this application can enhance the wettability of the separator to the electrolyte, ensuring uniform electrolyte distribution and optimizing the performance of the secondary battery.

[0094] In one embodiment of this application, the thickness of the first coating is 1 μm to 5 μm, preferably 1 μm to 2 μm. For example, the thickness of the first coating can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range consisting of any two of these values. Limiting the coating thickness to the range specified in this application is beneficial for promoting the removal of coordination solvents from active metal ions, increasing the rate of cross-interface transport of active metal ions, and improving the overall performance of the secondary battery.

[0095] In one embodiment of this application, the unit coating weight of the first coating is 0.1 g / m². 2 ~0.8g / m 2 The preferred value is 0.25 g / m 2 ~0.5g / m 2 For example, the unit coating weight of the first coating can be 0.1 g / m². 2 0.2g / m 2 0.3g / m 2 0.4g / m 20.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 Or it can be a range consisting of any two of these values. Limiting the unit coating weight of the first coating to the range specified in this application is beneficial for promoting the removal of coordination solvents from active metal ions, increasing the rate of cross-interface transport of active metal ions, and improving the overall performance of the secondary battery. It should be noted that the unit coating weight of the first coating in this application refers to the unit coating weight on the substrate side.

[0096] This application does not impose any particular limitation on the type of substrate, as long as it can achieve the purpose of this application. For example, the material of the substrate may include, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), glass fiber, polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), and polyamide (PA). The type of substrate may include, but is not limited to, at least one of woven membrane, nonwoven fabric, microporous membrane, composite membrane, rolled membrane, and spun membrane.

[0097] This application does not impose any particular limitation on the preparation method of the diaphragm, as long as it achieves the purpose of this application. For example, the preparation method of the diaphragm may include, but is not limited to, the following steps: coating a diaphragm coating slurry onto the surface of a substrate, and then drying it to obtain the diaphragm. This application does not impose any particular limitation on the coating method, as long as it achieves the purpose of this application. For example, the coating method may include, but is not limited to, wire rod coating, microgravure coating, or spray coating.

[0098] The fifth aspect of this application provides a negative electrode coating slurry comprising the adhesive described in the first aspect of this application.

[0099] In one embodiment of this application, the negative electrode coating slurry includes a negative electrode active material, a conductive agent, and a binder; based on the mass of the negative electrode coating slurry, the mass percentage of the adhesive is 0.58%~22.6%; the mass percentage of the negative electrode active material is 38.2%~49.1%; the mass percentage of the conductive agent is 0.2%~3.5%; and the mass percentage of the binder is 1.5%~4.5%. For example, the mass percentage of the adhesive can be 0.58%, 3%, 5%, 8%, 12%, 15%, 18%, 22.6%, or any combination of two of these values; the mass percentage of the negative electrode active material can be 38.2%, 40%, 42%, 45%, 47%, 49.1%, or any combination of two of these values; the mass percentage of the conductive agent can be 0.2%, 1%, 2%, 3%, 3.5%, or any combination of two of these values; and the mass percentage of the binder can be 1.5%, 2.5%, 3.5%, 4.5%, or any combination of two of these values. The negative electrode coating slurry obtained within the scope of this application, with its limited mass percentages of the adhesive, negative electrode active material, conductive agent, and binder, exhibits good dispersibility, stability, and ionic conductivity.

[0100] In this application, the types of negative electrode active materials, conductive agents, and binders are not limited. For example, negative electrode active materials may include, but are not limited to, silicon-carbon materials, carbon-based materials represented by hard carbon and graphite, cobalt oxide, and titanium-based oxides (Li4Ti5O). 12 Other silicon-based composite materials (BaFeSi / C composites); conductive agents may include, but are not limited to, common negative electrode conductive agents such as superconducting carbon, graphene, and carbon nanotubes; binders may include, but are not limited to, common negative electrode binders such as CMC, PAA, and SBR.

[0101] In this application, the aforementioned negative electrode coating slurry includes a solvent selected from at least one of deionized water, N,N-dimethylformamide (DMF), and N-methylpyrrolidone (NMP). It should be noted that the solvent in the negative electrode coating slurry is the same as that in the adhesive solution.

[0102] This application does not impose any particular limitation on the preparation method of the above-mentioned negative electrode coating slurry, as long as it can achieve the purpose of this application. For example, the preparation method of the negative electrode coating slurry may include, but is not limited to, the following steps: mixing the negative electrode active material, conductive agent, binder and the adhesive liquid described in the first aspect of this application in a specific mass ratio, adding deionized water as a solvent, adjusting to a slurry with a solid content of 49wt%, and stirring evenly in a vacuum mixer to obtain the negative electrode coating slurry.

[0103] A sixth aspect of this application provides a negative electrode sheet comprising the negative electrode coating slurry described in the fifth aspect of this application. The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer comprising the negative electrode coating slurry provided in the fifth aspect of this application. The negative electrode sheet made using the negative electrode coating slurry provided in this application exhibits good ionic conductivity, which can reduce battery internal resistance and improve charge / discharge efficiency.

[0104] In one embodiment of this application, the negative electrode sheet includes a negative current collector, a negative electrode material layer, and a coating layer. The negative electrode material layer is disposed on at least one surface of the negative current collector, and the second coating layer is disposed on at least one surface of the negative electrode material layer. The second coating layer includes the adhesive liquid described in the first aspect of this application.

[0105] In this application, the aforementioned "negative electrode material layer disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the negative electrode current collector, or only a portion of the surface area. This application has no particular limitation, as long as the purpose of this application is achieved. This application has no particular limitation on the negative electrode current collector, as long as the purpose of this application is achieved. For example, the negative electrode current collector can be copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel or foamed copper, aluminum foil, or a composite current collector. The aforementioned composite negative electrode current collector can be a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The material of the aforementioned polymer material base layer can be, but is not limited to, at least one of polypropylene (PP), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). The material of the aforementioned metal layer can be, but is not limited to, at least one of copper, copper alloy, nickel, and nickel alloy. This application does not impose any particular limitation on the thickness of the negative electrode material layer and the negative electrode current collector, as long as the purpose of this application can be achieved. For example, the thickness of the single-sided negative electrode material layer is 50 μm to 180 μm, and the thickness of the negative electrode current collector is 3 μm to 10 μm.

[0106] This application does not specifically limit the preparation method of the negative electrode sheet, as long as it achieves the purpose of this application. Exemplarily, the negative electrode sheet can be prepared by the following method: The above-mentioned negative electrode coating slurry is coated onto at least one surface of the negative electrode current collector, and after drying, a negative electrode sheet with a single-sided negative electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode current collector, and after drying, a negative electrode sheet with a double-sided negative electrode material layer is obtained. After coating, the negative electrode sheet is obtained by cold pressing and cutting. Exemplarily, the negative electrode sheet can also be prepared by the following method: Negative electrode active material, conductive agent, and binder are added to deionized water and stirred evenly to obtain a negative electrode slurry with a solid content of 45wt% to 70wt%. The negative electrode slurry is uniformly coated onto one surface of the negative electrode current collector, and after drying, a negative electrode sheet with a single-sided negative electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode current collector. After drying, a negative electrode sheet with a double-sided negative electrode material layer is obtained. After coating, it is cold-pressed and cut to obtain a negative electrode sheet with a negative electrode material layer. Then, the adhesive solution described in the first aspect of this application is applied to the surface of the negative electrode material layer of the above negative electrode sheet by spraying or micro-gravure coating. After coating, it is cold-pressed and cut to obtain a negative electrode sheet.

[0107] Example:

[0108] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0109] Test methods and equipment:

[0110] Test of the molar content of metal elements in metal-organic framework materials doped with metal elements:

[0111] The contents of framework metal Zr and metal element M in metal-organic framework materials doped with metal elements were determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The molar ratio of metal element M to Zr in the metal-organic framework material was calculated and denoted as d. Based on the amount of substance of the metal-organic framework material, the molar content of the metal element is represented by r, where r = 6d.

[0112] Specific procedures: Digest using BVIII grade nitric acid. Add 20 mg of sample and 15 mL of nitric acid to a polytetrafluoroethylene beaker. Heat at 80°C for 20 min. After the solvent has evaporated and about 2 mL remains, add 15 mL of nitric acid and continue heating for about 20 min. Repeat adding nitric acid until the solid is completely dissolved and the residual liquid is clear and transparent. Start removing the acid, dilute with ultrapure water, and inject the sample.

[0113] Testing the total defect rate Z of metal-organic framework materials doped with metal elements:

[0114] The total defect rate of metal-organic framework materials doped with metal elements was tested using thermogravimetric analysis (TGA) in a temperature range of 50℃-600℃, a heating rate of 3℃ / min, and an air atmosphere.

[0115] The results were processed as follows: The mass of the remaining material (zirconia-M) from the TGA test at 600℃ was used as a baseline, and normalization was performed, recorded as 100%. Under ideal conditions, in defect-free metal-organic framework materials, the chemical formula of the metal-doped metal-organic framework material at 350℃ is M. m O m / 2 Zr6O6(OL)6, the corresponding standardized weight is N (%), N (%) = MA (M m O m / 2 Zr6O6(OL)6) / MA(6ZrO2+M m O m / 2 )×100%, where MA(M m O m / 2 Zr6O6(OL)6) represents 1 mol M m O m / 2 The mass of Zr6O6(OL)6, MA(6ZrO2+M m O m / 2 () represents 6 mol ZrO2 and 1 mol M m O m / 2 The sum of their masses. At 350℃, the normalized weight of metal-organic framework materials doped with defective metal elements is less than N%, indicating insufficient internal OL connectors when defects are present. The total defect rate is calculated using the formula: Where w% (350℃) is the standardized weight of metal-organic framework material with defects at 350℃, i.e., w% (350℃) = weight of remaining material at test temperature of 350℃ / weight of remaining material at test temperature of 600℃, and Z is the total defect rate of metal-organic framework material with metal elements.

[0116] Testing the unsaturated coordination defect rate K of metal-doped metal-organic framework materials:

[0117] The unsaturated coordination defect rate of metal-doped metal-organic frameworks (MOFs) was determined using solid-state phosphorus NMR spectroscopy. The metal-doped MOFs were activated under vacuum at 150 °C for 4 h. 100 mg of 2,2,6,6-tetramethylpiperidine-1-oxygen radical (TMPO) was dissolved in 15 mL of dichloromethane to obtain a TMPO solution. 50 mg of the activated metal-doped MOFs were then immersed in the TMPO solution for 1 h. Defects in the metal-doped MOFs were labeled and identified using TMPO. The unsaturated coordination defect rate of the metal-doped MOFs was measured using a Bruker Avance NEO 600 MHz NMR spectrometer. A 3.2 mm MAS probe was used, with a rotation speed of 15 or 18 kHz. 31 The P signal was calibrated using the NH4H2PO4 signal. Peak fitting was performed on the data between 1 and 100 using Origin, and the fitted R value was... 2 ≥99.8%. The peaks near chemical shifts 62, 58, 55, and 53 represent Zr-blank, μ-OH(OL), μ-OH(sol), and Zr-sol sites, respectively. Zr-blank indicates an unsaturated coordination defect; μ-OH(OL) indicates a bridged hydroxyl group adjacent to the OL organic ligand; μ-OH(sol) indicates a bridged hydroxyl group adjacent to a coordination defect in a small molecule; and Zr-sol indicates a coordination defect in a small molecule. The relative proportions of the corresponding species can be obtained based on the peak area percentages.

[0118] Among them, the metal-organic framework material doped with metal elements has the molecular formula M m Zr6O4(OH)4(OL) 6-(x+y) / 2 (sol) x (blank) y N n In this calculation, the value of x is obtained by calculating the peak area ratio of μ-OH(sol) and Zr-sol species, and the value of y is obtained by calculating the peak area ratio of Zr-blank. The unsaturated defect rate is y / 12.

[0119] Counterion quantity b test:

[0120] 25 mg of metal-doped metal-organic framework material was added to 5 mL of NaOH solution with a concentration of 1 mol / L. The types and concentrations (mass fractions) of counterions in the sample solution were determined using an ion chromatograph (model: Dionex-7680). The mass fraction of the counterion is denoted as W(N), and the molar mass of the counterion is denoted as M(N).

[0121] The mass fraction of Zr in the metal-organic framework material doped with metal elements was determined to be W(Zr), and the molar mass of Zr was determined to be M(Zr) using inductively coupled plasma optical emission spectrometry (ICP-OES). The molecular formula of the metal-organic framework material doped with metal elements is M. a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b middle, .

[0122] Testing of the average particle size D of metal-doped metal-organic framework materials:

[0123] 2 mg of metal-doped metal-organic framework material was dispersed in 20 mL of methanol and sonicated for 20 min to 60 min. A portion of the suspension was then dropped onto a copper grid and dried. The average particle size of the sample was measured using a transmission electron microscope (TEM). The particle size of the metal-doped metal-organic framework material particles in the TEM image was measured using Processing-Velox software, and the average particle size was obtained by Gaussian fitting.

[0124] Test of the molar ratio of Zr to OL in the adhesive:

[0125] Zr content test in the adhesive solution: Take an adhesive solution sample weighing between 1.2 and 1.4 g. Considering the volume of the digestion vessel (the amount of sample added and acid added are limited), accurately weigh the sample and record its weight m. Divide the sample into 10 portions (record the weight of each of the 10 portions, with the largest portion used as a control vessel) and place them into 10 digestion vessels. Add 6 mL of concentrated nitric acid and 1 mL of 30% H2O2 solution to each of the 10 digestion vessels. Heat at 140℃ for 0.5 h (after the diaphragm has softened). Remove the heater, and then add 3 mL of 30% H2O2 solution to each digestion vessel. After cooling to approximately room temperature (or when it is not hot to the touch, the digestion vessels can be shaken appropriately during this period), add another 3 mL of concentrated nitric acid. Assemble the digestion apparatus and digest the sample according to the specific program. After digestion, combine the results in a 500 mL volumetric flask (PP material) and dilute to volume with ultrapure water. After adjusting the volume, shake well and then filter through a 0.22μm filter to obtain the prepared test solution.

[0126] (1) Open the instrument according to the operating procedure of the inductively coupled plasma atomic emission spectrometer. After the instrument is in a stable state, measure the standard curve solution. Plot the standard curve with zirconium ion concentration as the abscissa and the corresponding response value as the ordinate. The correlation coefficient r2≥0.9995.

[0127] (2) Under the same instrument conditions, the response value of zirconium ions in the test solution is measured, and the mass concentration (ug / mL) of the zirconium ions in the test solution is found on the standard curve. From this, the molar amount of Zr in the diaphragm can be calculated.

[0128] (3) The standard curve is tested by sequentially injecting samples from low concentration to high concentration. The standard solution and QC (initial calibration verification) are washed with water for 2 minutes before injection. The test solution needs to be washed with 5% nitric acid for 2 minutes and then washed with water for 2 minutes before injection.

[0129] Test for OL content in adhesive:

[0130] Sample pretreatment: 25 mg of sample was placed in 5 mL of NaOH aqueous solution (1 mol / L), sonicated for 1 h, and after complete decomposition of the gel sample, filtered and detected by liquid chromatography. Column: Agilent ZORBAX SB-C18 column, 4.6 x 150 mm, 5 μm; flow rate: 0.8 mL / min; injection volume: 10 μL; column temperature: 30°C; mobile phase elution program: gradient elution of 85% acetonitrile and 15% formic acid aqueous solution (0.1%), run time 12 min; detector: DAD, wavelength 230 nm, bandwidth 4 nm.

[0131] X-ray diffraction pattern test:

[0132] Metal-organic framework powder samples doped with metal elements were placed in the X-ray diffractometer stage. Using Cu target Kα rays and a scanning rate of 5° / min, with a scanning angle range of 2° to 40°, XRD patterns were obtained. The corresponding diffraction peaks were read and their positions recorded.

[0133] Testing the viscosity of the adhesive solution:

[0134] The viscosity of the adhesive solution was tested using a Brookfield dial rotational viscometer. First, the sample was placed in a container. Rotor #5 was selected, and the chosen rotor was screwed counter-clockwise onto the shaft connecting rod. The lifting knob was rotated to slowly lower the instrument, immersing the rotor in the sample until the liquid surface was just flush with the scale mark. The motor switch was turned on to start the rotor rotation, setting the speed to 20 rpm. After one minute, once the index stabilized, the viscosity of the sample was read. The viscosity of the freshly dispensed adhesive solution was tested using the above method and recorded as η0. Then, the viscosity of the adhesive solution after standing for 3 months was tested and recorded as η3. The viscosity change rate = (η3 - η0) / η0 × 100%.

[0135] Test of solid content difference:

[0136] Take a volume of adhesive solution at least 30 mm high and place it in a 50 ml centrifuge tube. Store it vertically and let it stand for 3 months. Then test the solid content in the top 10 mm and bottom 10 mm of the adhesive solution. Take a small amount of the top and bottom layers of the adhesive solution respectively and spread them evenly on a centrifuge tube with a mass of m. 上 and m 下 The total weights recorded on the aluminum foil are M. 上 and M 下 After baking in an oven at 120℃ for 30 minutes, the total weight of the aluminum foil was M' 上 and M' 下 The solid content of the upper layer adhesive was calculated to be (M'). 上 -m 上 ) / (M 上 -m 上 The solid content of the lower layer adhesive is (M')×100%. 下 -m 下 ) / (M 下 -m 下 )×100%, and the difference between the solid content of the upper layer and the solid content of the lower layer is denoted as △B.

[0137] Testing of particle size Dv50 of diaphragm coating slurry:

[0138] Weigh 1g of sample and mix thoroughly with 20mL of deionized water and a trace dispersant. Sonicate the mixture in an ultrasonic device for 5 minutes, then pour the solution into an SCF-126B sample introduction system for testing. The testing equipment used is an Omec LS-609 laser particle size analyzer. During the test, the particle size is measured by measuring the intensity of the scattered light as the laser beam passes through the dispersed particle sample. The data is then used to analyze and calculate the particle size distribution that forms the scattering spectrum. Each sample is tested three times, and the final particle size (Dv50) is obtained by averaging the three tests.

[0139] Viscosity test of diaphragm coating slurry:

[0140] The viscosity of the diaphragm coating slurry was tested using a BROOKFIELD dial-type rotational viscometer. The sample was placed in a 50mL centrifuge tube. A suitable rotor and rotation speed were selected according to the sample requirements (rotor #5, 100rpm). The selected rotor was screwed counterclockwise onto the shaft connecting rod. The lifting knob was rotated to slowly lower the instrument, gradually immersing the rotor into the liquid until the rotor level mark was level with the liquid surface. The level was then fine-tuned. The instrument was plugged in, and the speed control button was turned to the selected speed range. The pointer control lever was pressed to turn on the motor switch. The lever was then released, and the rotor began to rotate. The reading was taken after one minute when the pointer stabilized.

[0141] Viscosity = pointer reading × coefficient.

[0142] Diaphragm closed-cell temperature test:

[0143] Weigh 5mg of diaphragm sample and test the heat change of the sample during programmed temperature rise using a differential scanning calorimeter (DSC) to accurately determine the closed-cell temperature (i.e. the temperature point with the highest heat absorption rate). The test temperature range is 25~300℃, and the heating rate is 10℃ / min.

[0144] Membrane ionic conductivity test:

[0145] The ionic conductivity of the membrane was tested using electrochemical impedance spectroscopy. Four 20mm diameter discs were cut from the membrane material, and four 16mm diameter discs were prepared for the reaction.

[0146] Test steps: 1. Place the diaphragm into 4 fixtures in the glove box and assemble and seal them; 2. Place the diaphragm into the equipment (Yuaneng Technology-EIC1400M), set the pressure to 5kg, let it stand for 20min, set the EIS test parameters to 100000-100Hz, and then click Start Experiment; 3. Fit the EIS spectrum to obtain the ionic impedance of the diaphragm; 4. Repeat the above operation to test the EIS of layers 1 to 4 and fit the ionic impedance. Calculate the ionic conductivity of the diaphragm using the formula σ=d / (R×S).

[0147] Where σ is the ionic conductivity, R is the ionic resistance, S is the membrane area participating in the reaction, and d is the membrane thickness.

[0148] Differential scanning calorimetry (DSC) test:

[0149] 4 mg of negative electrode sheet and 5 μl of electrolyte were weighed and placed in a 27 μl Netzsch high-pressure crucible for DSC. The crucible was then sealed using a press to obtain the sample. Differential scanning calorimetry (DSC) was then performed on the sample using a Netzsch DSC214 differential scanning calorimeter. The heating range was 25 °C to 400 °C, and the heating rate was 10 °C / min. The peak value of the main exothermic peak was recorded, i.e., the heat flow per unit mass, in mW / mg. The peak area from 150 °C to 350 °C was calculated to obtain the heat of exothermic reaction from 150 °C to 350 °C, in J / g. A smaller peak value indicates better flame retardant performance of the battery, a less severe thermal runaway, and a lower risk of explosion / combustion.

[0150] The electrolyte is composed of organic solvents ethylene carbonate (EC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), and lithium salt lithium hexafluorophosphate (LiPF6). The mass ratio of EC:EMC:DMC in the electrolyte is 2:1:7, and the concentration of LiPF6 is 1 mol / L.

[0151] Example 1-1:

[0152] Preparation of Zr-based metal-organic framework material

[0153] Add 21.38 g (85.8 mmol) of zirconium oxynitrate hydrate and 23.31 g (128.7 mmol) of 2-aminoterephthalic acid into a 1000 mL two-neck flask, then add 205 mL of deionized water and 81 mL of glacial acetic acid. Reflux at a stirring rate of 600 rpm / min and a temperature of 100 °C for 24 hours, and then centrifuge at 10000 r / min for 60 min to separate the crude product of the metal-organic framework material.

[0154] Wash the crude product of the metal-organic complex. The specific steps are as follows: soak in ethanol for 12 h, soak in acetone for 12 h, soak in dichloromethane for 12 h, then soak in ethanol for 12 h, soak in acetone for 12 h, soak in dichloromethane for 12 h. Totally soak in different liquids for 6 times, and centrifuge at a rate of 10000 r / min for 15 min to separate the Zr-based metal-organic framework material.

[0155] Preparation of metal element-doped Zr-based metal-organic framework material

[0156] Add 1 g of lithium nitrate and 30 g of water into a 350 mL pressure-resistant bottle to obtain a metal salt solution, then add 7.75 g of the above Zr-based metal-organic framework material, and ultrasonically mix for 20 min. Heat at 100 °C for 6 h to obtain a second suspension. Centrifuge the second suspension at 10000 r / min for 5 min to obtain a solid substance. Wash the solid substance with water 5 times and dry it in vacuum at 120 °C for 12 h to obtain the metal element-doped Zr-based metal-organic framework material Li 0.3 Zr6O4(OH)4(OL) 4.266 (CH3COO - ) 0.216 (blank) 3.252 (NO3) 3.552 .

[0157] The above-prepared metal element-doped Zr-based metal-organic framework material Li 0.3 Zr6O4(OH)4(OL) 4.266 (CH3COO - ) 0.216 (blank) 3.252 (NO3) 3.552The total defect rate was 30.7%, the unsaturated defect rate was 27.1%, the average particle size was 70 nm, the molar content of the metal element Li was 0.3 mol / mol, sol was acetate, and the dicarboxylic acid conjugated organic ligand OL was 2-aminoterephthalate, meaning the molecular skeleton of the dicarboxylic acid conjugated organic ligand was phenyl, and the functional group was amino. The metal-doped metal-organic framework materials used in the other examples are similar to the Li... 0.3 Zr6O4(OH)4(OL) 4.266 (CH3COO - ) 0.216 (blank) 3.252 (NO3) 3.552 The preparation is similar, and will not be described in detail in this application.

[0158] <Preparation of Adhesive Solution>

[0159] A 0.015 g / mL LiOH solution was added to the metal-doped Zr-based metal-organic framework material prepared above to neutralize it. 6.4 g of the above neutral metal-doped Zr-based metal-organic framework material (Li...) was then weighed out. 0.3 Zr6O4(OH)4(OL) 4.266 (CH3COO - ) 0.216 (blank) 3.252 (NO3) 3.552 Place the solution in a flat-bottomed flask, dissolve 0.3g of polyvinylpyrrolidone (PVP-K30) in 68g of deionized water, and dissolve 0.1g of sodium dodecyl sulfate (SDS) in 10g of deionized water. Mix the two solutions and add them to the flat-bottomed flask. Use an ultrasonic cleaner (Kunshan Shumei Ultrasonic Instrument Co., Ltd., model KQ-500VDE) and a mechanical stirrer (Aika Instrument Equipment Co., Ltd., model IKA RW20 digital) to stir and sonicate at 360r / min for 3h to obtain the adhesive solution. The ultrasonic parameters are: power 100W, frequency 40kHz. Based on the mass percentage of the adhesive solution, the mass percentage of metal-organic framework material doped with metal elements is 7.5%, the mass percentage of dispersant is 0.35%, and the mass percentage of wetting agent is 0.12%.

[0160] Examples 1-2 to 1-13:

[0161] Except for adjusting the relevant parameters in <Preparation of Zr-based metal-organic framework materials doped with metal elements> so that the prepared metal-doped metal-organic framework materials are as shown in Table 1, the rest is the same as in Example 1-1.

[0162] Examples 1-14 to Examples 1-16:

[0163] Except for adjusting the relevant parameters in <Preparation of Zr-based metal-organic framework materials doped with metal elements> to make the molar content of metal elements as shown in Table 1, the rest is the same as in Example 1-1.

[0164] Examples 1-17 to 1-22 and 1-27:

[0165] Except for adjusting the relevant parameters in "Preparation of Zr-based Metal-Organic Frameworks Doped with Metal Elements" to obtain the metal-doped metal-organic frameworks as shown in Table 1, the rest is the same as in Examples 1-1. Specifically, in Examples 1-17, the dicarboxylic acid conjugated organic ligand OL is 2,5-pyridinedicarboxylic acid; in Examples 1-18, the dicarboxylic acid conjugated organic ligand OL is imidazole-4,5-dicarboxylic acid; in Examples 1-19, the dicarboxylic acid conjugated organic ligand OL is 2,5-difluoroterephthalic acid; and in Examples 1-20, the metal-doped metal-organic frameworks... In the metal-organic framework materials, the dicarboxylic acid conjugated organic ligand OL in Examples 1-21 is 2,5-dimethoxyterephthalic acid; in the metal-doped metal-organic framework materials of Examples 1-22, the dicarboxylic acid conjugated organic ligand OL in Examples 1-22 is 2,5-dichloroterephthalic acid; and in the metal-doped metal-organic framework materials of Examples 1-27, the dicarboxylic acid conjugated organic ligand OL is terephthalate.

[0166] Examples 1-23 to 1-26:

[0167] Except for adjusting the relevant parameters in <Preparation of Zr-based metal-organic framework materials doped with metal elements> so that the total defect rate, unsaturated defect rate and average particle size of the prepared metal-organic framework materials are as shown in Table 1, the rest are the same as in Example 1-1.

[0168] Examples 1-28:

[0169] Except for replacing lithium nitrate with lithium chloride in the <Preparation of Zr-based metal-organic framework materials doped with metal elements>, so that the prepared metal-doped metal-organic framework materials are as shown in Table 1, the rest is the same as in Example 1-1.

[0170] Examples 1-29:

[0171] Except for replacing lithium nitrate with lithium sulfate in the <Preparation of Zr-based metal-organic framework materials doped with metal elements>, so that the prepared metal-doped metal-organic framework materials are as shown in Table 1, the rest is the same as in Example 1-1.

[0172] Examples 1-30 to 1-31:

[0173] Except for adjusting the mass percentage of Zr-based metal-organic framework material doped with metal elements in the adhesive solution as shown in Table 1, the rest is the same as in Example 1-1.

[0174] Examples 1-32:

[0175] Except for replacing the metal element-doped Zr-based metal-organic framework material with the Zr-based metal-organic framework materials shown in Table 1 in the <Preparation of the Glue> section, the rest is the same as in Example 1-1.

[0176] Example 2-1:

[0177] <Preparation of Diaphragm Coating Slurry>

[0178] 0.1g of sodium carboxymethyl cellulose (CMC(PR)) was dissolved in 10.28g of deionized water, and 4.82g of polyacrylate (LCH107 (19.8%), Meishan Yindile Technology Co., Ltd.) was added to form a premix. The premix was then added to the adhesive solution prepared in Example 1-1, and the mixture was stirred at 360r / min and sonicated for 2h using an ultrasonic cleaner and a mechanical stirrer to obtain the diaphragm coating slurry. The ultrasonic parameters were: power 100W, frequency 40kHz. Based on the mass percentage of the diaphragm coating slurry, the mass percentage of the adhesive solution was 84.8%, the mass percentage of the water-retaining agent was 0.1%, and the mass percentage of the binder was 4.82%.

[0179] <Preparation of the diaphragm>

[0180] The above-mentioned diaphragm coating slurry was uniformly coated onto one side of a 9 µm thick polyethylene (PE) porous substrate (the PE porous substrate was provided by Shenzhen Xingyuan Material Technology Co., Ltd., model SW509I) using a micro-grooving method. The slurry was then dried at 90°C to obtain a diaphragm with a single-sided coating. The coating thickness was 2 μm, and the coating weight per unit area was 0.5 g / m². 2 .

[0181] Examples 2-2 to 2-4:

[0182] Except for the application of the adhesive solutions prepared in Examples 1-14 to 1-16 in the <Preparation of Diaphragm Coating Slurry>, the rest of the process is the same as in Example 2-1. Example 2-2 uses the adhesive solution prepared in Examples 1-14, Example 2-3 uses the adhesive solution prepared in Examples 1-15, and Example 2-4 uses the adhesive solution prepared in Examples 1-16. The scanning electron microscope images of the diaphragm coatings in Examples 2-2 to 2-4 are shown below. Figures 1 to 3 As shown.

[0183] Example 3-1:

[0184] Except for the different adhesive used in the <Preparation of Diaphragm Coating Slurry>, the adhesive used in Example 3-1 is the same as that in Example 1-1. The adhesive used in Example 3-1 is the same as that in Example 1-1, except that a neutralizing agent is not added to adjust the acidity or alkalinity of the Zr-based metal-organic framework material doped with metal elements.

[0185] Examples 3-2 to 3-3:

[0186] Except for the preparation of the diaphragm coating slurry, in which the mass percentage of the metal-organic framework material doped with metal elements in the adhesive solution and the mass percentage of the solvent are adjusted according to Table 4, the rest is the same as in Example 2-1.

[0187] Examples 3-4 to 3-5:

[0188] Except for the following in <Preparation of Diaphragm Coating Slurry>, where the mass percentage of the adhesive solution is adjusted according to Table 4, the mass percentage of the solvent in the diaphragm coating slurry is changed accordingly, and the percentages of other components in the diaphragm coating slurry remain unchanged, the rest is the same as in Example 2-1.

[0189] Examples 3-6 to 3-8:

[0190] Except for adjusting the coating thickness and unit coating weight according to Table 4 in the <Preparation of the Separator> section, the rest is the same as in Example 2-1.

[0191] Example 4-1:

[0192] <Preparation of Negative Electrode Coating Slurry>

[0193] The adhesive solution prepared in Example 1-1, graphite as the negative electrode active material, Super P as the conductive agent, sodium carboxymethyl cellulose (CMC) as the binder, styrene-butadiene rubber (SBR) as the binder, and deionized water were mixed and stirred at 360 r / min for 2 h using a mechanical stirrer to obtain the negative electrode coating slurry. Based on the mass of the negative electrode coating slurry, the adhesive solution had a mass percentage of 10%; the negative electrode active material had a mass percentage of 45%; the conductive agent had a mass percentage of 2%; the binder had a mass percentage of 2.5%; and the mass ratio of sodium carboxymethyl cellulose (CMC) to styrene-butadiene rubber (SBR) was 1:1.

[0194] <Preparation of Negative Electrode Sheets>

[0195] The above-mentioned negative electrode coating slurry was uniformly coated onto one surface of a 9μm smooth copper foil current collector and dried at 85℃ to obtain a negative electrode sheet with a single-sided negative electrode material layer. The coating weight of the negative electrode material layer was 186 g / m². 2 Then, the above steps are repeated on the other surface of the smooth copper foil current collector to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After drying at 85°C, it is rolled and then dried in a vacuum drying oven at 85°C for 12 hours. Finally, it is die-cut to obtain a negative electrode sheet with a size of 58mm×74mm for later use. The thickness of the single-sided negative electrode material layer is 60μm.

[0196] Examples 4-2 to 4-3:

[0197] Except for adjusting the relevant parameters according to Table 5 in <Preparation of Negative Electrode Coating Slurry>, the rest is the same as in Example 4-1.

[0198] Example 5-1:

[0199] <Preparation of Negative Electrode Sheets>

[0200] A slurry with a solid content of 50 wt% was prepared by adding graphite (anode active material), Super P (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) to deionized water at a mass ratio of 94.5:2:2:1.5. The slurry was then stirred evenly in a vacuum mixer to obtain the anode material layer slurry. This slurry was uniformly coated onto one surface of an 8 μm thick copper foil used as a cathode current collector and dried at 85°C to obtain a single-sided coated anode electrode. The above steps were then repeated on the other surface of the copper foil to obtain a double-sided coated anode electrode, which was then cut into 180 mm × 160 mm anode sheets for later use.

[0201] The adhesive solution prepared in Example 1-1 was then uniformly sprayed onto the surfaces of the two negative electrode material layers of the aforementioned negative electrode sheet using a spraying device to form a coating. After drying at 85°C for 0.5 hours, the coating was rolled and then die-cut to obtain a negative electrode sheet with dimensions of 58mm × 74mm. The thickness H of the single-sided negative electrode material layer was 45μm, and the compaction density of the negative electrode material layer was 1.55g / cm³. 3 The coating thickness h is 1.35 μm, and the compaction density of the coating is 1.55 g / cm³. 3 .

[0202] Examples 5-2 to 5-3:

[0203] Except for adjusting the relevant parameters according to Table 6 in the <Preparation of Negative Electrode Sheet>, the rest is the same as in Example 5-1. That is, the coating of Example 5-2 is prepared from the adhesive solution of Examples 1-30, and the coating of Example 5-3 is prepared from the adhesive solution of Examples 1-31.

[0204] Comparative Examples 1-1 to 1-8:

[0205] Except for adjusting the relevant parameters according to Table 2, the rest is the same as in Example 1-1.

[0206] Comparative Example 2-1:

[0207] Except for the fact that no slurry was coated on the substrate in the <Preparation of the Separator> section, the rest is the same as in Example 2-1.

[0208] Except for the adhesive used in the <Preparation of Diaphragm Coating Slurry>, the adhesive used in Comparative Example 2-1 is the same as that in Example 1-1, except that an undoped Zr-based metal-organic framework material is used instead of a metal-doped Zr-based metal-organic framework material.

[0209] Comparative Example 5-1:

[0210] Except for the fact that the above-mentioned negative electrode coating slurry was not sprayed on the surface of the negative electrode material layer in the <Preparation of Negative Electrode Sheet>, the rest is the same as in Example 5-1.

[0211] The preparation and performance parameters of each embodiment and comparative example are shown in Tables 1 to 6.

[0212] Table 1:

[0213]

[0214] Note: " / " indicates no relevant parameters, Z (%) represents the total defect rate of metal-organic framework materials doped with metal elements, K (%) represents the unsaturated defect rate of metal-organic framework materials doped with metal elements, D (nm) represents the average particle size of metal-organic framework materials doped with metal elements, and Zr:OL refers to the ratio of the amount of Zr to the amount of dicarboxylic acid conjugated organic ligand in metal-organic framework materials doped with metal elements.

[0215] Table 2:

[0216]

[0217] Table 3:

[0218]

[0219] Table 4:

[0220]

[0221] Note: " / " indicates no relevant parameters; "W1" indicates the mass percentage of metal-organic framework material doped with metal elements based on the mass of the adhesive; "W2" indicates the mass percentage of the adhesive based on the mass of the diaphragm coating slurry.

[0222] Table 5:

[0223]

[0224] Table 6:

[0225]

[0226] As can be seen from Examples 1-1 to 1-31 and Comparative Examples 1-1 to 1-8, by using the metal-doped metal-organic framework material of this application, and by controlling the type and molar content of the metal element, the average particle size of the metal-doped metal-organic framework material, and the mass percentage of the metal-doped metal-organic framework material, dispersant, and wetting agent in the adhesive solution within the range of this application, the resulting adhesive solution exhibits a low viscosity change rate and solid content difference, indicating that the obtained adhesive solution has good dispersibility and uniformity. When the content of the metal-doped metal-organic framework material in the adhesive solution is too small, as in Comparative Example 1-1, although the adhesive solution also has a low viscosity change rate and solid content difference, it is not conducive to the subsequent preparation of the separator and negative electrode sheet. When the content of the metal-doped metal-organic framework material in the adhesive solution is too small, there is more solvent in the adhesive solution, which increases the cost of the adhesive solution and makes it difficult to homogenize the separator coating slurry and the negative electrode coating slurry.

[0227] The type of organic ligand affects the viscosity, viscosity change rate, and solid content difference of the adhesive. As can be seen from Examples 1-1, 1-17 to 1-22 and 1-27, by adjusting the type of organic ligand within the scope of this application, the resulting adhesive has a lower viscosity change rate and solid content difference, indicating that the resulting adhesive has better dispersibility and uniformity.

[0228] The type of counterions affects the viscosity, viscosity change rate, and solid content difference of the adhesive. As can be seen from Examples 1-1, 1-28, and 1-29, by controlling the type of counterions within the scope of this application, the resulting adhesive has a lower viscosity change rate and solid content difference, indicating that the resulting adhesive has better dispersibility and uniformity.

[0229] As can be seen from Examples 2-1 to 2-4, Examples 3-1 to 3-8, and Comparative Example 2-1, the absence of the membrane coating slurry of this application on the substrate results in a lower ionic conductivity of the membrane. Using the adhesive solution of this application to prepare the membrane coating slurry and then the membrane, a membrane coating slurry with a suitable Dv50 and a membrane with a suitable pore-closing temperature and high ionic conductivity can be obtained, thus resulting in a secondary battery with better overall performance.

[0230] The type of metal-organic framework material doped with metal elements in the adhesive affects the pore-closing temperature and ionic conductivity of the diaphragm. As can be seen from Examples 2-1 to 2-4, by controlling the type of metal-organic framework material doped with metal elements in the adhesive within the scope of this application, a diaphragm coating slurry with a suitable Dv50 and a diaphragm with a suitable pore-closing temperature and high ionic conductivity can be obtained. Figures 1 to 3 Scanning electron microscope (SEM) images of the diaphragm coatings in Examples 2-2, 2-3, and 2-4, respectively. Figures 1 to 3 As can be seen, the coating coverage is 100% and the coating is uniform; Figure 4 The XRD patterns of the metal-organic framework materials doped with metal elements used in Examples 2-2 and 2-3, and the undoped metal-organic framework materials, are shown below. Figure 4 As can be seen from the data, the metal-organic framework materials doped with metal elements all include diffraction peaks of the (200) and (111) crystal planes, indicating that the metal-organic framework materials used in the above embodiments still have good crystal structure after being loaded with metal elements.

[0231] The acidity or alkalinity of the metal-organic framework material doped with metal elements affects the pore-closing temperature and ionic conductivity of the membrane. As can be seen from Examples 2-1 and 3-1, by controlling the metal-organic framework material doped with metal elements in the adhesive solution to be neutral, a membrane coating slurry with a suitable Dv50 can be obtained, and the resulting membrane has a suitable pore-closing temperature and high ionic conductivity.

[0232] As can be seen from Examples 2-1, 3-2 to 3-8, by limiting the mass percentage of the metal-organic framework material doped with metal elements, the mass percentage of the adhesive solution, the coating thickness and the unit coating weight within the scope of this application, a membrane coating slurry with a suitable Dv50 and a membrane with a suitable pore-closing temperature and high ionic conductivity can be obtained, thereby obtaining a secondary battery with good overall performance.

[0233] As can be seen from Examples 4-1 to 4-3, Examples 5-1 to 5-3 and Comparative Example 5-1, the negative electrode sheet containing the adhesive of this application has a lower heat flow and heat release per unit mass. This indicates that the battery containing the negative electrode sheet of this application has better flame retardant performance, less severe thermal runaway, and a lower risk of explosion / combustion.

[0234] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A liquid adhesive, characterized in that, It includes a metal-organic framework material, a dispersant, and a wetting agent; the molecular formula of the metal-organic framework material is M. a Zr6O m (OH) n (OL) 6-(x+y) / 2 (sol) x (blank) y N b , 0≤a≤2.3, 4≤m≤6, 0≤n≤4, 0.09≤x≤0.92, 3≤y≤6.02, 0.9≤b≤9.24; wherein, M is a metallic element, including at least one of Li, Na, K, Ca, Mg, Cu, Co, Ni, Fe, Cr, Ti, Zn, and Mn; OL is a dicarboxylic acid conjugated organic ligand, the molecular skeleton of which includes any one of phenyl, imidazolyl, and pyridyl; sol includes acetate, formate, and CH3-(CH2). p -COO - At least one of them, 1≤p≤6, blank is a ligand vacancy, and N is a counterion; Based on the mass of the adhesive, the mass percentage of the metal-organic framework material is 5% to 10%; the mass percentage of the dispersant is 0.1% to 1%; and the mass percentage of the wetting agent is 0.1% to 1%.

2. The adhesive liquid according to claim 1, characterized in that, In the adhesive solution, the molar ratio of Zr to OL is 6:(2.766~4.329).

3. The adhesive liquid according to claim 1, characterized in that, In the adhesive solution, the molar ratio of Zr to OL is 6:(2.766~4.266).

4. The adhesive liquid according to claim 1, characterized in that, In the adhesive solution, the molar ratio of Zr to OL is 6:(2.766~3.69).

5. The adhesive liquid according to claim 1, characterized in that, In the adhesive solution, the molar ratio of Zr to OL is 6:(2.766~3.5).

6. The adhesive liquid according to claim 1, characterized in that, In the adhesive solution, the molar ratio of Zr to OL is 6:(2.766~2.94).

7. The adhesive according to claim 1, characterized in that, The total defect rate of the metal-organic framework material was found to be 29.6% to 53.5% by thermogravimetric analysis.

8. The adhesive according to claim 7, characterized in that, The total defect rate of the metal-organic framework material is 40% to 53.5%.

9. The adhesive liquid according to claim 7, characterized in that, The total defect rate of the metal-organic framework material is 42% to 53.5%.

10. The adhesive according to claim 7, characterized in that, The total defect rate of the metal-organic framework material is 45% to 53.5%.

11. The adhesive according to claim 7, characterized in that, The total defect rate of the metal-organic framework material is 49% to 53.5%.

12. The adhesive liquid according to claim 1, characterized in that, The unsaturated coordination defect rate of the metal-organic framework material was found to be 26.1% to 50.1% by solid-state NMR phosphorus spectroscopy.

13. The adhesive according to claim 12, characterized in that, The unsaturated coordination defect rate of the metal-organic framework material is 37%~50.1%.

14. The adhesive according to claim 12, characterized in that, The unsaturated coordination defect rate of the metal-organic framework material is 40%~50.1%.

15. The adhesive according to claim 12, characterized in that, The unsaturated coordination defect rate of the metal-organic framework material is 42%~50.1%.

16. The adhesive according to claim 12, characterized in that, The unsaturated coordination defect rate of the metal-organic framework material is 45%~50.1%.

17. The adhesive according to claim 1, characterized in that, 0.1≤a≤2.3。 18. The adhesive according to claim 1, characterized in that, The dispersant includes at least one of polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylonitrile; the wetting agent includes at least one of 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,2-hexanediol, 1,2-octanediol, 2-methyl-2,4-pentanediol, 1,3-butanediol, sodium dodecyl sulfate, sodium dodecyl sulfonate, and kyne glycol polyoxyethylene ether.

19. The adhesive according to claim 1, characterized in that, The metal-organic framework material is neutral.

20. The adhesive liquid according to claim 1, characterized in that, The molecular skeleton of the dicarboxylated conjugated organic ligand is selected from phenyl, and the dicarboxylated conjugated organic ligand includes functional groups, which include any one of amino, hydroxyl, mercapto, methoxy, nitro, fluorine, and chlorine groups.

21. The adhesive according to claim 1, characterized in that, The dicarboxylic acid conjugated organic ligand includes any one of terephthalate, amino-modified terephthalate, fluoroterephthalate, and pyridinic acid dicarboxylate.

22. The adhesive liquid according to any one of claims 1 to 21, characterized in that, The average particle size of the metal-organic framework material is 20 nm to 110 nm.

23. The adhesive liquid according to any one of claims 1 to 21, characterized in that, The average particle size of the metal-organic framework material is 64 nm to 80 nm.

24. A method for preparing the adhesive liquid according to any one of claims 1 to 23, characterized in that, include: The dispersant, the wetting agent, the metal-organic framework material, and the solvent are mixed and dispersed evenly to obtain the adhesive solution.

25. A diaphragm coating slurry, characterized in that, It includes a water-retaining agent, an adhesive, and an adhesive solution according to any one of claims 1 to 23.

26. The diaphragm coating slurry according to claim 25, characterized in that, Based on the mass of the diaphragm coating slurry, the mass percentage of the adhesive is 80%~90%; the mass percentage of the water-retaining agent is 0.1%~1%; and the mass percentage of the binder is 1%~5%.

27. The diaphragm coating slurry according to claim 25, characterized in that, The water-retaining agent includes sodium carboxymethyl cellulose, and the binder includes at least one of polyacrylate, ethyl acrylate copolymer, butyl acrylate copolymer, styrene acrylate copolymer, acrylamide acrylate copolymer, maleic anhydride acrylate copolymer, vinylpyrrolidone acrylate copolymer, methyl methacrylate acrylate copolymer, acrylonitrile acrylate copolymer, vinyl alcohol acrylate copolymer, sodium carboxymethyl cellulose, and polyvinyl alcohol.

28. The diaphragm coating slurry according to claim 25, characterized in that, The viscosity of the diaphragm coating slurry is 20cps to 100cps.

29. The diaphragm coating slurry according to claim 25, characterized in that, The viscosity of the diaphragm coating slurry is 40 cps to 80 cps.

30. A diaphragm, characterized in that, It includes a substrate and a first coating disposed on at least one surface of the substrate, the first coating being prepared from the diaphragm coating slurry of any one of claims 25 to 29.

31. The diaphragm according to claim 30, characterized in that, The thickness of the first coating is 1μm to 5μm.

32. The diaphragm according to claim 30, characterized in that, The unit coating weight of the first coating is 0.1 g / m². 2 ~0.8g / m 2 .

33. The diaphragm according to any one of claims 30 to 32, characterized in that, It meets at least one of the following characteristics: (1) The thickness of the first coating is 1 μm to 2 μm; (2) The unit coating weight of the first coating is 0.25 g / m. 2 ~0.5g / m 2 .

34. A negative electrode coating slurry, characterized in that, The adhesive comprising any one of claims 1 to 23.

35. The negative electrode coating slurry according to claim 34, characterized in that, The negative electrode coating slurry includes a negative electrode active material, a conductive agent, and a binder; based on the mass of the negative electrode coating slurry, the mass percentage of the adhesive is 0.58%~22.6%; the mass percentage of the negative electrode active material is 38.2%~49.1%; the mass percentage of the conductive agent is 0.2%~3.5%; and the mass percentage of the binder is 1.5%~4.5%.

36. A negative electrode sheet, characterized in that, It is prepared from the negative electrode coating slurry as described in claim 34 or 35.

37. A negative electrode sheet, characterized in that, The present invention includes a negative electrode current collector, a negative electrode material layer, and a second coating layer, wherein the negative electrode material layer is disposed on at least one surface of the negative electrode current collector, and the second coating layer is disposed on at least one surface of the negative electrode material layer, and the second coating layer is prepared by the negative electrode coating slurry according to claim 34.

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